Cryogenic switch



July 1, 1969 T. G. CROW 3,

CRYOGENIC SWITCH Filed Sept. 13, 1967 L LOAD Thomas G. Crow,

INVENTOR.

United States Patent 3,453,446 CRYOGENIC SWITCH Thomas G. Crow, Orlando, Fla., assignor to the United States of America as represented by the Secretary of the Army Filed Sept. 13, 1967, Ser, No. 667,883 Int. Cl. H01h 51/34, 37/00; G05t' N US. 'Cl. 307-98 2 Claims ABSTRACT OF THE DISCLOSURE A system for rapidly switching high currents. A storage inductor is connected in a parallel combination with a load, and the combination is connected in series with a conductor in a cryogenic environment, and an energy source. When the conductor is warmed, the storage inductor discharges into the load.

Background of the invention This invention is in the field of high current switches.

High currents may be switched into loads in at least two ways, depending in the energy source providing the current. A large capacitor may be charged, and suddenly discharged to yield a high current into a load. Or, a current may be established in a large inductor, with the inductor being suddenly connected to the load, to provide a large current. Of these two schemes, the inductive storage scheme oifers at least one advantage. An inductor is able to store a much larger amount of energy than a capacitor, for a given volume. An inductive storage system has the disadvantage of requiring the interruption of high currents (in a particular application, currents as high as 200,000 amperes). The interruptions of large currents bring the known problems of high current switching, such as establishment of arc across relatively movable switch contacts (and the attendant dissipation of power in the switch), and slow break times (because of the arc). High power tubes may be used, but have relatively high internal impedances. The invention overcomes these disadvantages.

Summary of the invention The invention is a high current switch system. The system employs special switch means connected in series with a load and a power supply. An inductive storage element is connected in parallel with the load, and discharges into the load when the switch means is operated. The switch means includes a conductor, in a cryogenic environment, in series with a first switch, and connected in parallel with a second switch. Charging current for the storage element is provided through the second switch, with the first switch open. When the first switch is closed, and the second switch is opened, the charging current flows through the conductor in the cryogenic environment, and causes 1 R (resistive) warming of the conductor. As the conductor warms, its resistance has a large relative increase. This resistance increase brings about a rise in voltage across the conductor and the storage element. When the voltage reaches a high enough value, the load will conduct, and the energy in the storage element will provide a large current through the load. The load may be high energy flash tube, or some similar load which has a high impedance with no current flowing, but which begins to conduct as some voltage level, and then has a low impedance.

The invention, by using the charge in resistance of the conductor, is able to switch high currents, without the establishment of arcs, and without the problems arising from such arcs. Since no arc is established, switching may 3,453,446 Patented July 1, 1969 be rapid, and no energy is wasted in maintaining an arc.

An object of this invention is to provide a novel current-switching circuit.

Another object is to provide a cryogenic switch circuit.

A further object is to provide a switch circuit using a conductor in a cryogenic environment, with switching accomplished by warming the conductor.

These objects, and others which may be obvious to one skilled in the art, may be realized by the invention as described hereinafter, with the accompanying drawing.

Brief description of the drawing The single drawing figure is a schematic diagram of the invention.

Description of the preferred embodiment Referring now to the drawing, reference letter B designates a power supply, which may take the form of a battery. The battery is connected in series with the parallel combination of switches S1 and S2. Switch S1 is connected in series with a conductor 3, which conductor is maintained at a cryogenic temperature, as by being enclosed in a container, dotted-line rectangle 4-), with liquid hydrogen, or some other cryogenic fluid. An inductive storage element L is connected in a parallel combination with a load (5), with this combination in series with battery B and the other parallel combination.

Operation of the invention is as follows: Initially, both switches (S1 and S2) are open, no current is flowing in the circuit, and no energy is stored in L. To charge L, switch S2 is closed. Current then flows through L, and builds up in the well-known manner. When a discharge of L into load '5 is desired, switch S1 is closed, and switch S2 is opened. Obviously, the circuit current then flows through S1 and conductor 3. Heavy current through 3 causes I R heating therein (since 3 still has some resistance, even at cryogenic temperatures). As 3 warms, its resistance rapidly increases (relative to its cryogenic resistance). As 3 increases in resistance, a voltage is developed thereacross and across inductor L. When the voltage reaches a high enough level, load 5 will conduct, and L will discharge into the load.

In summary, a charging switch (S2), when closed, allows charging of inductive storage element L by battery B. When shunt switch S1 is closed, and S2 is opened, the charging current is diverted through S1 and conductor 3. As the current flows through 3, it (3) warms up, and has a rapid, large increase in resistance. This increasing resistance produces a voltage across the resistance and across the storage element, and the voltage eventually discharges through the load. A rapid discharge is produced, and little energy is dissipated outside of the load.

While a specific embodiment of the invention has been disclosed, other embodiments may be obvious to one skilled in the art, in light of this disclosure, but may still be within the scope of the invention. For example, switches S1 and S2, while shown as mechanical switches, could obviously be solenoid operated, or could be replaced by such devices as controlled rectifiers, ignitrons, etc. Also, conductor 3 may be warmed by external means, rather than its own 1 R heating, or this PR heating may be augmented by external means. Also, inductance L may be maintained at a cryogenic temperature, if desired for space considerations. Further, battery B may be replaced by rectified and filtered A-C.

I claim:

1. An energy discharge circuit including: an inductive storage element; load means connected in parallel with said storage element; cryogenic switch means having a first and a second terminal; charging means having a third and a fourth terminal; first and second switches; one end 3. 4 of the parallel combination of said load means and said 2,748,315 5/1956 Martinet a1 315290 X storage element connected to said first terminal, and the 3 1 5 53 1 5 Harpley X the other end of said parallel combination connected to 3 191 074 6/1965 Carruthers et a1 3O7 1O4 said third terminal; said first switch connected between said fourth and said first terminals; said second switch 5 3215925 11/1965 Rieke 3O798 X connected between said fourth and said second terminals. ,2 1 9 NeWhOU e et a1. 307245 X 2. The circuit as defined in claim 1 wherein said switch 3,372,306 3/1968 Koizumi 31798 X means includes a conductor in a cryogenic environment.

References Cited UNITED STATES PATENTS 2,276,851 3/1942 LiVingStOIl 307104 X 2,313,961 3/1943 Oglesbee 315-290 X 7 ROBERT K. SCHAEFER, Primary Examiner.

10 T. B. JOIKE, Assistant Examiner.

U.S. Cl. X.R.v 

